The surgical procedures of endoscopy, including laparoscopy, with or without videoscopy, are in common use at the present time. The primary advantage of a laparoscopy is that only a small incision is required to access an area where a wide range of surgical procedures can be performed through the small incision with minimal morbidity. Until the present invention, access to the peritoneal cavity during laparoscopy has been gained by the use of a trocar assembly, i.e. a surgical instrument comprising two major components, a trocar (obturator) and a cannula (trocar tube), as described below. The distal end of the cannula of the trocar assembly is blunt and therefore relies on the ability of the trocar to pierce the various layers of the anterior abdominal wall to gain access to the peritoneal cavity. Traditionally, in preparation for a laparoscopy, a small incision corresponding in size to about the diameter of the cannula, is made in the skin and underlying tissues down to and sometimes including an even smaller incision in the anterior fascial sheath sufficient in size to accommodate the tip of the trocar. A Veress needle is then inserted through the incision and underlying tissues into the peritoneal cavity, the peritoneal cavity is insufflated with CO.sub.2 gas, and the Veress needle is withdrawn from the peritoneal cavity prior to insertion of the trocar assembly. The distal end of the trocar disposed within the cannula is then placed so that it is in contact with the layers of the body wall exposed by the incision and the trocar is inserted through the tissues. By applying pressure against the proximal end of the trocar, the sharp pointed distal end of the trocar is forced through the different layers of the abdominal wall until it enters the peritoneal cavity carrying the cannula with it. The trocar is then withdrawn, leaving the cannula as an access-way to the peritoneal cavity. Various types of surgical and video instruments are inserted through the cannula into the peritoneal cavity permitting many kinds of surgical procedures to be performed within a patient's abdomen.
There are a number of disadvantages associated with the use of conventional laparoscopic trocars. The principal disadvantages are firstly that significant initial force is usually required to insert the trocar through the layers of the anterior abdominal wall and secondly, that it is a "blind" procedure. The initially applied force may result in the trocar being inadvertently inserted further into the abdominal cavity than is necessary or desirable, and it is not at all unusual in such a situation for the trocar to result in an injury to a major blood vessel or to other visceral organs in the patient's abdomen. These injuries may be of a serious nature, and may even be fatal.
As used below, the term trocar refers to a solid sharp pointed instrument or obturator which is inserted through a trocar tube or cannula, a cannula being a hollow sheath or sleeve, which is capable of receiving surgical instruments, equipment for endoscopic visualization and videoscopy and gas or liquid. The term "distal end" applied to an instrument refers to the end of the instrument that is introduced into the body, and the term "proximal end" refers to the end that remains outside the body during the procedure.
The development and widespread use of trocars for endoscopy has served to focus on the shortcomings and problems to be solved in the design of devices used for accessing body cavities, including the abdominal cavity. Although there have been many modifications and improvements in their design, the problems discussed above have not been overcome. An example of such a modification is a trocar having a retractable sleeve. As soon as the sharp tip of the trocar enters the peritoneal cavity, a spring mechanism should cause the sleeve to snap over the sharp tip of the trocar and in this way prevent injury to any organs that the trocar tip contacts. However, this mechanism may fail. As a result of the force applied to the trocar, the trocar tip pushes the peritoneum ahead of it, and causes forward "tenting" of the peritoneum before and while the tip penetrates the peritoneum. As penetration occurs, the peritoneum surrounding the trocar tip so closely embraces the trocar tip that the passage of the sleeve through the hole in the peritoneum is prevented or delayed. If the sleeve fails to cover the entire tip of the trocar as it penetrates the peritoneum, injuries to intra-abdominal organs by the trocar tip or its sharp beveled edges will not be prevented.
Although trocar assemblies have been modified in various ways, no device has been disclosed using only a cannula, i.e. without a trocar, to gain access to the abdominal cavity. U.S. Pat. No. 5,147,376 discloses a trocar needle having a threaded truncated cone bit having a cutting blade with a rounded edge at its truncated cone end. U.S. Pat. No. 4,191,191 describes an elongated sharp pointed instrument for insertion through an elongated cannula, the sharp pointed instrument having screw threads at its tip, and the proximal portion of the instrument including a crank assembly. U.S. Pat. No. 5,217,441 describes a trocar penetration depth indicator having two threaded sleeves through which a trocar is inserted. U.S. Pat. No. 5,258,003 discloses a trocar which is inserted through a cannula, the trocar having a tapered distal end with screw threads formed on the outer surface of the distal end. The distal end terminates in a flexible tip, through which a hollow needle passes. The needle communicates with a means for indicating changes in pressure as the distal end of the needle enters the peritoneal cavity. U.S. Pat. No. 5,209,736 describes a trocar assembly device including an outer, larger diameter trocar tube and an inner, smaller diameter trocar tube, which extends distally beyond a distal end portion of the outer trocar tube. The distal end of the inner smaller trocar tube is tapered, the tapered end bearing threads on its outer surface to facilitate insertion of the trocar through the layers of the body.
In the above-mentioned patents and in currently used instruments, the trocar or the instrument within the cannula pierces or cuts the body layers and gains access to the peritoneal cavity. Furthermore, the progress of the trocar is achieved as a result of a force that is applied to the proximal end of the trocar, the force being applied substantially perpendicular to the skin surface through which the trocar passes, and the cannula is introduced with the trocar through the hole created by the trocar. The pointed trocar is one of the principal causes of injuries to abdominal viscera during laparoscopy, as described above.
The principal object of the present invention is to provide a safe, easy-to-use, easy-to-maintain and inexpensive apparatus for, and method of, gaining access to body cavities for endoscopic procedures which avoids the above-described disadvantages presented by currently known devices.
Another object of the invention is to provide a cannula for the purpose of accessing the peritoneal cavity, wherein the distal end of the cannula comprises a means for cutting and penetrating the layers of the body wall to gain entry into the peritoneal cavity, without the need for a trocar.
A further object of the invention is to provide a method for inserting the cannula through the abdominal wall and into the peritoneal cavity whereby the progress of the cannula occurs via rotational movement through the layers of the body wall including the peritoneum, rather than by a force applied at substantially 90.degree. to the body wall. This rotational entry of the cannula substantially lessens the potential for damage to the tissues and organs during endoscopy.
The present invention has advantages relating to environmental issues, more specifically to the disposal of used and contaminated cannulae and the cost thereof. Disposal of a cannula made from environmentally friendly, biodegradable materials is simple and inexpensive. Furthermore, the reusable form of the cannula or a portion thereof is safe for use after sterilization, and decreases the enormous number of used contaminated instruments which must be disposed of.